Carbon black is generally used as a rubber reinforcing filler. However when using rubber containing carbon black as a tire tread, there are problems because resistance to rolling is increased and fuel consumption is increased.
On the other hand, with the improvement of automobile performance, the grip performance required for a tire has become more severe. As a conventional technique for solving these problems, it is known to use silica (white carbon) as a filler.
However, with filling silica, there arose problems with the reduction of rolling resistance. Also grip performance is not sufficient and the viscosity of the rubber and silica during kneading is high. Furthermore, the processability is insufficient, resulting in a deterioration of productivity.
An object of the present invention is to provide an aluminum hydroxide which can be used as a filler that can improve processability and productivity during kneading with a rubber for use as a tire tread while providing a sufficient reinforcing effect such as sufficient grip performance. It is another object of the present invention to provide a sufficient rolling resistance reduction effect when used as a filler in a rubber composition for a tire tread.
Under these circumstances, the present inventors have done intensive research in order to accomplish the above object. As a result, it has been found that aluminum hydroxide having a specific particle size, a specific BET specific surface area and a specific pore size can be used as a filler that satisfies the above object in whole or in part. It has also been found that this aluminum hydroxide can be obtained by mixing and neutralizing a basic solution and an acidic solution, one or both of the solutions containing an aluminum ion, under high-speed rotary shear stirring. Thus, the present invention has been accomplished.